I would like to know your suggestion on what additionally I can write on ?? operator, Doesn't this enough to get you understand the whole idea behind ?? operator ? or you want to go beyond the code and want to know the operation takes place at compiler, and assembly level ?

I have a certain hesitation to use nullable basic value types. I think a more realistic szanario of the ?? operator is with Linq queries, e.g., ...FirstOrDefault() ?? myDefault.
And in the same go, the default(T) operator could have been mentioned. That's another construct that is relatively little known. The default(T) comes into play with that particular Linq function FirstOrDefault(...).
Cheers
Andi